In hospitals and other medical facilities, Radio Frequency Identification (RFID) tags are attached to medical items to provide the following general functions: (1) identifying medical items or other resources that enter a room or other space in a medical facility; (2) determining where those medical items or other resources came from; and (3) determining whether those medical items or other resources were consumed during a medical procedure performed in the room or space. Generally, each medical item pulled for use during a particular medical procedure includes an MD tag affixed to the item's outer packaging. These RFID tags contain appropriate inventory information regarding each item as maintained in the inventory control system of the medical facility. Generally, each individual item can be tracked through use of the RFID tags and appropriate REID reader technology.
When scanning RFID tags of medical items consumed during a medical procedure, it is important to avoid unintentional “stray reads” of tags on items that are not consumed during the procedure. To avoid stray reads, some prior systems implement short range RFID readers operating in low-frequency (LF) or high-frequency (HF) bands that read tags at distances of less than about 1 meter. When using such systems, the user must bring the RFID tag into close proximity with the sensing antenna.
One disadvantage of the LF and HF systems is their relatively low data transfer rate. For inventory control purposes that call for higher data transfer rates, it is desirable to use ultrahigh frequency (UHF) RFID readers. However, due to the longer-range sensitivity of UHF systems, stray reads can become a problem when such systems are used in environments that are not completely electromagnetically sealed, such as an enclosure that has an opening to allow materials to pass into or out of the enclosure.
What is needed, therefore, is a shielded enclosure that, though not being completely electromagnetically sealed due to the necessity of an access opening, prevents stray RFID signals from entering the opening and being detected inside the enclosure.